Burette



May 16, 1939. M. FA BETzoLD ET AL BURETTES 2 Sheets-Sheet l Filed Feb.l8, 1956 llllll H tllf May 16, 1939.

M. F. BETzoLD vf-:T AL 2,158,102

BURETTES Filed Feb. 18, 1936 2 Sheets-Sheet 2 Patented May 16, 1939UNITED STATES PATENT OFFiCE BURETTE nois Application February 18, 1936,Serial No. 64,478

6 Claims.

The present invention relates to burettes and has for one of its objectsthe provision of an automatic burette which is of simple and efficientform, with an accurate Zero point, and provided with means forpreventing evaporation from the solution in the reservoir to: which itis connected, when the burette is not being used.

Another object of this invention is to provide in a burette means formore eciently filling the same and for preventing the accumulation ofthe liquid in the overflow chamber.

Another object of this invention is to provide in a device of thischaracter a detachable overflow chamber provided with an integralair-cleaning and purifying chamber for ltering (and purifying) air (byremoving dust and carbon dioxide) which moves into and out of theoverflow chamber and burette. This simplifies cleaning of the overflowchamber and also the manufacture thereof. The overflow chamber may alsobe sealed to the burette and a detachable air purifying chamber may beprovided.

More particularly, an object of this invention is to provide arestriction in the overflow tube which carries liquid from the overflowchamber back into the receptacle whereby on filling the burette thegraduated tube of the burette will be filled rst instead of the overowtube, as in prior constructions.

Specifically, the restriction used in the overflow tube is preferablyone of capillary dimensions, whereby the flow of the fluid upwardlythrough the overflow tube during filling of the burette is materiallyslowed down so that the graduated tube is filled before the overow tubecan be lled. While not absolutely necessary, it is preferable to alsoprovide an expansion chamber in the overow tube above the restrictedportion. The expansion chamber also serves to take expansion andcontraction in the overflow tubes.

Another object of this invention is to provide a constriction in saidrestriction at one point at least whereby to retard the upward flow ofliquid through the overflow tube to such an extent that it is possibleto lill the burette before the liquid, which also rises into theoverflow tubes, fills the expansion chamber.

Another object of this invention is to provide a valve of simpleconstruction adapted to connect lthe graduated burette tube with theconduit leading to the liquid in the bottle or flask containing theliquid with which the burette is to "be lled or alternately connect theburette tube iwith-theoutlet conduit from which the desired amount ofliquid is withdrawn into a beaker or the like, as is customary whenusing devices of this character.

A further object of this invention is to provide a simple valvestructure for controlling the flow of the air which is pumped into theburette to raisethe liquid from the bottle into the burette and to cutolf this flow if and when desired and also exhaust the air at the propertime.

A still further object of this invention is to provide a metal alloyplug valve or the like for the burette which will not corrode and doesnot stick in the glass seat with which it cooperates, the alloy beingsuch as not to be affected by alkaline solutions, whereby to preventvalve from sticking and leaking. Such a plug does not need a lubricantbut is sufciently lubricated by the solution which is used in theburette, thus preventing contamination of the solution by a foreignlubricant which can work into the apparatus and coat the insidesthereof, making the burette less easy to read.

Other objects of this invention will appear hereinafter as thedescription thereof proceeds, the novel features, arrangements andcombinations being clearly set forth in the specification and the claimsthereunto appended.

In the drawings:

Fig. l is a front elevational view partly in section of a buretteembodying our invention;

Fig. 2 is a cross-section of the upper part of the burette;

Figs. 3 and 4 show different valve positions for one of the valvesembodied in this invention; and

Fig. 5 shows a modification of our invention which is shown partly insection for the sake of clearness.

In certain types of-burettes there is provided an overflow chamber atthe top thereof and an overflow tube leading therefrom back into theliquid container upon which the burette is supported and with which theburette is adapted to have communication. The overflow chamber isnecessary in o-rder to secure a zero point for the burette to vtherebyeliminate one meniscus reading. This overflow tube has communication atall times with the liquid in the bottle or flask and, therefore, whenthe liquid is being forced upwardly under air pressure into the burettethe liquid also flows upwardly through the overflow tube and, in flowingupwardly through the overflow tube, the rate of travel of the liquid ismuch greater than the rate of flow of the liquid through the burrettetube. That is, the level of a volume of liquid in the overflow tuberises very much more rapidly than in the graduated burette tube. Theresult is that the liquid reaches the overow chamber and may even iiowout of same through the air cleaner inlet. This, of course, would not bedesirable and under no conditions is it desirable Vto have the overflowchamber filled with the liquid since it would make it more diiicult toobtain the zero point and this liquid might partially evaporate so thatthe concentration of the liquid is increased when the liquid returns tothe bottom. This invention contemplates for one of its objects,providing a simple, yet effective, means for preventing the flow ofliquid in the overflow tube from reaching the overflow chamber when theburette is being lled. We will now proceed to describe our improvedburette construction.

In the drawings, I6 represents a bottle, iiask or similar receptaclecontaining the liquid with which the burette is to be filled. This isprovided with a rubber stopper II having a central opening for receivingthe outer conduit I2 on the lower portion of the burette. Alternativelythe connection with the bottle may be made by means of a ground glassjoint. It is through this tube that the air is introduced into thebottle I0, the air traveling downwardly through the outer tube andoutwardly through the opening I3 above the liquid level in the bottle.The lower end of the burette is also provided with an inner conduit I4through which the liquid travels upwardly under pressure into theburette tube I 5 and overow tube I6, this conduit and the outer conduitI2 being joined in sealed relation as at IT.

Communicating with the outer conduit I2 is a laterally extending conduitI8 which has a three-way valve I9 arranged therein and also a suitableair-cleaning material, such as soda lime, such as indicated at 20, andwhich is well known in this art. Air under pressure is introduced intothe conduit I8 by means of the bulb 2l in the manner which is wellunderstood in this art.

The valve I9 is of the ordinary plug type and is provided with adiametrically arranged passage 22 which extends through the plug and isadapted, as is shown in Fig. l, to permit the now of air through theconduit I8. This valve Yalso has a lateral passage 23 communicating withthe passage 22 whereby air may be exhausted into the atmosphere if andwhen desired through the exhaust conduit 24, the valve being arranged asillustrated in Fig. 4 for this purpose. In Fig. 3, the valve is shownarranged to cut off the return of the air from the conduit I2 throughthe conduit I8.

Mounted on the top of an inner conduit I4 is a valve casing 25, theinner surface of whichis substantially conical in shape to receive theconical plug 26 which is rotatable therein, the latter having anoperating handle 2'I formed thereon. This plug valve 26 is made of glassor of a suitable material, such as silver or metallic alloys or otherlike material, which are resistant to the action of the liquids to besupplied to the burette, such as acids, alkalies, and oxidizing andreducing agents in solution.

We have found that an alloy having the approximate composition set forthherebelow is hard and suitable for this type valve and when ground intothe glass seat in the burette provides a close-tting valve and one whichwill not corrode. Silver, being soft, does not permit grinding of thevalve into its seat as easily as the hard valves are capable of having.This alloy given as an example has the following approximatecomposition:

Per cent Nickel 56 Chromium 24 Copper 8V Molybdenum 4 Tungsten 2Manganese 1% The graduated burette tube I5 is mounted on top of thevalve casing 25 and has a conduit 28 at the lower end thereofcommunicating with the interior of the casing 25. The valve casing 25also is provided with an outlet tube 29 and the valve 26 has twodiagonally extending, diametrically arranged passages 36 and 3I whichoperate in the following manner. valve 2l in the position illustratedliquid may ilow into the graduated burette tube from the bottle I0 orflow from the bottle I0 into the graduated burette tube, or vice. versa.When the valve is turned to a position, from the position shown, thevalve passage 3I connects the burette with the outlet tube 29 to permitthe contents of the graduated burette tube to be drained therefrom asdesired, and in the quantities required. It will be noted that the valvecasing 25 forms a connecting medium for the graduated burette tube,conduit I4 and outlet tube 29 and also forms a supporting means forI theburette tube I5.

Integrally formed .on the upper end of the burette tubeV I5 is a taperedoutlet 3I, the inner diameter of which is very small and tapering downto capillary proportions at the tip thereof. The tapered outlet 3| isarranged within an overflow chamber 32 and it will be noted from Figs. land 2 that the outlet is curved in a direction toward the left wall ofthe overflow chamber so that liquid emerging therefrom will be directedagainst that wall and flow down the side of that wall into the upper end33 of the overflow tube, without first falling on the bottom of thechamber 32.

The outlet end of this tube is drawn down to approximately a 0.5 mm.opening whereby the flow of the solution out of same is at a high rateof speed, whereby upon closing the valve 26 all of the solution outsidethe end of this tube continues its motion in a direction against thewall of the over-flow tube, thus preventing any drops from clinging tothe tube which may be drawn back into the burette when the solution isbeing withdrawn from the burette at the lower end thereof. The accuracyof the zero point is therefore greater and tests revealthat the accuracyis within .01 ml.

The upper'end 33 of the overow tube is connected to the lower end 34 ofsame by means of an expansion chamber 35. Just below the expansionchamber 35 the overiiow tube is reduced considerably in diameter Vso asto provide a passage 36 having practically capilliary dimensions. Thiswill restrict the ow of fluid through the overflow tube andr in order toadditionally restrict the iiow, we propose to form the constriction 31in the restricted tubular portion 36 to make the passage at this pointeven smaller so that liquid will flow past this point but at anextremely slow rate, even when the liquid is under The bottom 38 of theoverflow chamber 32 slopes downwardlytoward the overow tube 33 wherebyany liquid which may at any time be With the plug Y in the overflowchamber will drain back into the overflow tube I6 and from there backinto the bottle I through the inner conduit i4 with which the overowtube IE has constant communication. The overflow tube also has alaterally and then downwardly extending integral tube 39 through whichair enters and exhausts and on the end of this tube there is placed anair-cleaning and purifying chamber 49 having a rubber stopper d! iittingsnugly in the neck thereof and having a central opening through whichthe tube 39 extends. The air cleaner 40 comprises a chamber filled witha suitable air-cleaning and purifying medium, such as soda lime, thelower end of the chamber containing glass wool 42, or the like, whichpermits the air to pass into and out of' the tube 39, but prevents thecleaning and purifying material from escaping. To prevent clogging ofthe chamber 49 there is provided an outlet tube 49' which has an outletand 4I communicating with the atmosphere and an inner end formed in theshape of a hook 42 so that it will not collect moisture descendingthrough the chamber 49, but will permit air to pass into and out of thechamber 49. Any moisture collects in the bottom where the steel wool ispresent and by having the upper end of the outlet tube 49 above theglass wool the moisture does not prevent the free ingress and egress ofthe air.

It will be understood that, except for the rubber Stoppers, the bulb 2l,metal valve 26, aircleaning material, etc., the parts are allconstructecl of glass, as is customary with instruments of this nature.rIhe burette operates as follows:

Assuming that all of the liquid is still in the bottle lil and there isno pressure in the burette, the operator turns the valve I9 into theposition illustrated in Fig. 1. I-Ie then proceeds to pump air into theconduit I8 by pressing on the bulb 2l, from whence it passes throughconduit l2 and opening I3 in the bottle il), as previously described.The pressure of the air on the upper surface of the liquid forces theliquid upwardly through the conduit i4, some of the liquid then passingupwardly through the overflow tube ll and some into the burette tube l5through the passage 30. Due to the small diameter of the overflowconduit the liquid level rises rapidly therein and if not restrained theliquid will ll the overflow chamber 35 before the graduated burette tubeis filled. However, due to the restricted portions 35 and 31, the flowof the liquid is immediately retarded when the liquid level reachesthese restricted portions and the liquid flows very slowly intoexpansion chamber 35. The liquid level in the burette continues to riseat the same, or at even a greater rate, and soon becomes higher than theliquid level in the everiiow tube. Finally the liquid lls the burettetube and is discharged through the outlet 3l against the side wall ofthe chamber 32. This liquid then drains back into the overflow tube aspreviously described. Even using appreciable air pressures, it has beenfound in actual tests that the restrictions 36 and 3l' so restrict theflow of the liquid that, while the liquid level may reach therestrictions before the burette tube l5 is even one-tenth iilled,nevertheless the ow is so cut down thereafter that the burette tubebecomes entirely lled, at least before the expansion chamber 35 becomesfilled with a liquid. In fact, ordinarily the expansion chamber is lessthan one-half full when the graduated burette tube is filled, even usinghigh pressures.

It will be obvious that with this arrangement, it is possible to fillthe burette without the necessity oi Watching same closely, as has beennecessary with previous devices, or by using low air pressures and,substantially the only liquid reaching the overflow chamber 32 is thatwhich enters through the outlet 3l.

It is not necessary to continue pumping air all the time until theburrette tube is filled. It is only necessary to introduce a. sufficientquantity of air into the bottle under pressure to cause the tube to beiilled if no more air is introduced. Consequently, long before theburette tube is filled the operator can turn the valve I9 into theposition shown in Fig. 3 so that the air in the burette will be retainedtherein and any air in the bulb 2l will be exhausted through the outlet24. When the burette tube has been completely filled, then the valve I9is turned into the position shown in Fig. 4, thus permitting the air inthe bottle to escape until the air pressure in the bottle issubstantially atmospheric. After this the liquid in the overflow tubeand overow chamber flows downwardly, as previously described, into thebottle. Valve I9 is then turned int'o the position shown in Fig. 3 toprevent contamination of the solution by carbon dioxide in the air andto prevent evaporation from the solution which increases theconcentration of the solution.

Of course, before turning the valve i9 to permit the air to escape fromthe apparatus the valve 26 is turned to prevent any or" the liquid inthe burette tube l5 from iiowing back into the bottle. a position 90from that illustrated. After the air has been exhausted from theapparatus, desired quantities of the liquid may be withdrawn by turningthe valve 2E to a position 180 from that illustrated. This positions thepassage 3| in communication with the conduit 28 and permits the liquidto flow out of the burette through the outlet tube 29.

In Fig. 5, we have illustrated a modied form of our invention which canbe used with a burette of the type illustrated in Fig. 1 or other typesof burettes in which the liquid may flow out of the overflow chamberthrough an outlet tube 44. In this form of the invention the overflowchamber 45, which is similar to that illustrated in Fig. 1, is providedwith a central opening at the bottom thereof and a rubber cork 46, orthe like, is iitted into that passage which also has a central openingtherethrough to receive t'he upper end of a burette tube 4l, so that theoverflow chamber may be detachably mounted on the burette tube, asillustrated. Also in this form of the invention, the tube 48 whichpermits the entrance and exit of the air has integrally connectedtherewith a cup-shaped portion 49 which is adapted to contain theair-filtering and purifying medium soda lime 43. Since the overflowchamber 45 can be inverted, after being removed from the burette, it isan easy proposition to fill the integral cupshaped portion 49 with theair-cleaning material. The cup-shaped portion may be closed by means ofa rubber stopper 5l having a small outlet tube 52 formed with a hookportion 52 similar to 42 in Fig. 2, extending through said stopper topermit the air to ent'er and leave the cup-shaped portion and overflowchamber. Glass wool 42 is provided at the top and bottom of cup-shapedportion 49, the lower layer collecting the moisture as in Fig. 2. Theoverflow chamber 45 may This can be done by turning the valve to beconnected to the tube '44 which drains back into some suitablereceptacle or may be connected Yas shown in Fig. 1 toan expansionchamber, such as 35, by means of a suitable length of rubber tubing orthe like. The advantage of this construction is that it permits theoperator to clean the overflow chamber very readily and, in View of theintegral cup-shaped air-cleaning material receiving chamber 49, thedevice is more readily constructed and does not require a .separatereceptacle, such as 40, in Fig. l.

The burette illustrated can be completely closed to the outer atmosphereexcept through the soda-lime chamber and this prevents the evaporationof portions of the solution and consequently the concentration is notincreased. Since the air does not circulate freely through the soda-limechamber there is little possibility of evaporation at this point. Aircirculates through this chamber only when the burette is being filled oremptied but not when the burett'e is not in use. It is during theperiods when the burette is idle and lled with a solution thatevaporation occurs mostly.

Obviously, those skilled in the art to which this invention pertains maymake various changes in the particular arrangement and construction ofthe parts illustrated in the embodiments of our invention shown anddescribed herein without departing from the Yspirit of this inventionand, therefore we do not wish to be limited except as hereinafter setforth in the claims.

Having thus fully described our invention-what We claim and desire tosecure by Letters Patent of the United States is:

1. A burette comprising a valve casing, a valve rotatable therein, agraduated burette tube supported on said valve casing directlythereabove, and a pair of conduits on the opposite side of' said casingspaced longitudinally thereof, one of said conduits being adapted to beconnected with the source of liquid supply and the other comprising adischarge conduit, passages in said valve adapted to selectively connectsaid burette Ytube with either one or the other of said conduits, and anoverflow conduit having continuous communication with the conduitthrough which liquid is supplied to said burette tube and with the upperend oi said burette tube through an opening in the upper end of thelatter, and independently of said valve, said overflow tube having anexpansion chamber therein and a constriction of relatively smallinternal diameter below said expansion chamber.

2. A burette comprising a valve casing, a valve rotatable therein, agraduated burette tube supported on said valve casing directlythereabove, and a pair of conduits on the opposite side of said casingspaced longitudinally thereof, one of said conduits being adapted to beconnected with the source ofV liquid supply and the other comprising adischarge conduit, passages in said valve adapted to selectively connectsaid burette tube with either one or the other of said conduits, and anoverflow conduit having continuous communication with the conduitthrough which liquid is supplied to said burette tube and with the upperend of said burette tube through an openl ing in the upper end of thelatter, and independently of said valve, said overflow tube having anexpansion chamber near the upper end Vthereof and a restricted openingof relatively small diameter immediately below said expan-A sionchamber.

3. In a burette of the class described, the combination with a burettetube, of an overflow chamber, an overflow conduit for draining theoveriiow fluid back into a receptacle with which the same is adapted tobe connected, a supply conduit for supplying both said burette tube andsaid overflow conduit while the former is being llecl, and a restrictedportion in said overiiow conduit of an internal diameter, substantiallyless than the normal diameter of said overflow conduit and ofsubstantially capillary proportions, said overflow conduit having anexpansion chamber arranged therein above said restricted portion.

4. A burette comprising a burette tube, an overflow conduitcommunicating with the upper end of said tube, a conduit for supplyingliquid to said burette tube, and an air-pressure conduit adapted to bearranged inV communication with a liquid receptacle, means for forcingair into said air-pressure conduit and a valve in said airpressureconduit adapted to selectively open and close said air-pressure conduitor discharge air from said air-pressure conduit into the atmosphere asdesired. Y

5. A burette comprising a burette tube having an air-cleaning andpurifying chamber in sealed relation therewith, said chamber having anair exit at its lower side and an outlet tube arranged Within saidchamber in sealed relation with the chamber and communicating with saidexit, the upper end of said outlet tube extending upwardly intoI saidchamber and being bent outwardly and then downwardly and terminatingsubstantially above the bottom of said chamber.

6. A buretteV comprising a burette tube, an overflow tube, a conduitadapted to be connected with a receptacle in which there is a source ofliquid supply for iilling said burette tube, a valve for connecting anddisconnecting said conduit and tube, an air-pressure inlet for creatingpressure on the liquid to be supplied to said tube, means for openingandV closing said inlet, and an outlet for iluid in said tube adapted tobe selectively opened and closed by said valve, said means for closingsaid air inlet also preventing entrance or escape of air from the liquidreceptacle to which the burette is connected.

MAX F. BETZOLD. CHARLES RASCHER. CHARLES A. TORP.

